1. Field of the Invention
The present invention generally relates to a device for filtering solids from a slurry of liquid and solids.
2. State of the Art
It is known to use a filter press to filter solids from a slurry of liquid and solids. A conventional filter press includes a plurality of filter plates which have filter media affixed thereto. The filter plates are slidably disposed on horizontal rails supported between the head end and the ram end of the press. The filter press further includes a hydraulic closing device to force the plates into abutting relationship with each other to form a stack near the head end of the press. The hydraulic closing device includes a follower which is movably disposed on the horizontal rails and connected to a hydraulic ram piston. The ram piston is slidably disposed in a hydraulic cylinder, and the hydraulic cylinder is connected to a pump to pump hydraulic fluid into the cylinder. Hydraulic fluid pumped into the hydraulic cylinder urges the follower against the stack of filter plates to hold the plates in abutting relationship with each other.
When slurry is pumped into the filter press and through the filter media on the plates, solids collect on the media, and filtered liquid flows through the media and from the press. When substantial quantities of solids have collected on the media, the solids must be removed and disposed of. To permit removal of solids from the media, the follower is moved away from the plates to the ram end of the press thereby creating a space between the plates and the follower. Each plate is then transported along the rails from the stack of filter plates to the follower end of the press while solids are dislodged from the media by conventional means.
A commonly employed means to transport the plates along the rails includes carriages connected to chains which slide along the rails. The carriages selectively couple to and uncouple from each filter plate.
Thus it can be seen that in operation the carriages couple to the first plate in the stack, and are driven by the chains to transport the plate to the follower end of the press to deposit it there. The carriages then return to the stack to couple to the next plate, and so forth.
Is is known to employ means to control the travel of the carriages along the rails. For example, British Pat. No. 934,772 teaches an electrically operated control system to control the flow of hydraulic fluid to a hydraulic cylinder. A hydraulic ram is reciprocatably disposed within the hydraulic cylinder, and the hydraulic ram is connected to gears which are in turn connected to chains to which the carriages are affixed. The electrically operated control system controls the flow of a stream of hydraulic fluid to the hydraulic cylinder to drive the ram. As the ram reciprocates within the cylinder, the gears are driven to move the carriages along the rails. When the carriages have carried a filter plate to the follower end of the press, the control system reverses the direction of travel of the ram thereby causing the carriage to travel back along the rails to couple to the next plate.
It should be understood that many liquids processed in a filter press generate explosive fumes. Electrical control systems such as the patented system identified above, generally can produce sparks which can ignite the explosive fumes. In a filter press which is used to filter liquids which generate explosive fumes, it is undesirable to utilize an electrically operated system. However, a hydraulically operated system can be used safely.
Conventional filter press shifting devices often include an electric motor which is manually controlled to drive the carriages. Such conventional shifting devices are often modified to operate automatically by the inclusion of an appropriate control system. Modificational of a conventional press to include the patented control system described above requires that a hydraulic cylinder and substantial gear train be substituted for the prior electric motor. On the other hand, applicant's control system includes a simple hydraulic motor which can be substituted for the electric motor.